The standard automobile distributor typically comprises a stator in the form of a cast housing, a support member, such as a plate, within the housing for carrying such elements as the breaker points, condensor and wiper, a rotor shaft extending through the housing and through the support plate, and a rotor assembly which is carried by the shaft. The breaker points which are mounted within the housing comprise a spring biased arm carrying one of two metallic electrodes which intermittently contact one another as an octagonal cam on the distributor shaft rotates past and in contact with the arm. In this fashion, ignition timing pulses are generated in proportion to engine speed.
This well known prior art breaker points design has provided reasonable satisfactory service for years. However, it is well known that the mechanical breaker points deteriorate with time until ignition performance is so poor that the breaker points must be replaced. Such deterioration is due partly to the foul atmospher in which the distributor is normally located, but is due largely to the physical deterioration of the electrode surfaces which results from the transfer of electrical impulses between two surfaces over long period of time. This deterioration affects not only engine performance, but gas mileage and exhaust emission levels.
To alleviate the aforementioned problems which do not use the mechanical-contacting breaker points, there have developed in the prior art an electromagnetic apparatus for generating ignition timing pulses by passing a metallic rotor through an air gap between a pair of inductively linked coils. The rotor of such an electromagnetic system operates as a shutter or interrupter and has a plurality of circumferentially spaced conductive teeth. This shutter is normally secured to the distributor rotor shaft in a predetermined angular position relative to the coils which are carried by the stator or nonrotating portion of the distributor assembly. To install the shutter member and coil set into the distributor normally involves careful placement so as to ensure that the proper timing is achieved. Many of the prior art disclosures at least suggest that a completely customized distributor assembly is required. Accordingly, installation does not appear to be easily carried out by the ordinary automobile owner. Moreover, such prior art ignition systems, while doing away with breaker points, remain totally dependent on vacuum-type spark advance devices to vary dwell angle or engine timing under all conditions.